Bile salts were previously thought to be end products of cholesterol metabolism but recent studies in animals and men have established the presence of bile salt sulfate esters. Sulfation may play an important role in detoxifying the potential hepatotoxicity of certain bile salts. Despite the pathophysiological significance of bile salt sulfation, the site and mechanism by which these sulfates are formed has not been determined. We have identified an enzyme from rat liver and kidney, bile salt sulfotransferase, which sulfates bile salts. The investigator proposes to purify and characterize this enzyme from rats and guinea pig liver using the techniques of ammonium sulfate fractionation, ion exchange column chromatographies isoelectrofocusing electrophoresis, and affinity chromatographies. The purified enzyme will be characterized with respect to substrate specificity, kinetic properties, pH profile and molecular weight. The purity of the enzyme will be checked with disc gel electrophoresis, ultracentrifuge sedimentation analysis and immunological cross reaction. Studies will also be conducted to investigate the regulation (uptake, transformation and excretion) of bile salt sulfation in an isolated hepatocyte system. Effects of steroid hormones and ethanol on the bile salt sulfation will be investigated. If the evidence of inhibition is observed, the nature of this inhibition will be further studied. These studies are designed to provide important basic information about our understanding of bile salt sulfation.